Process for improving the handle of polyethylene terephthalate fabrics with an alkali metal hydroxide and specific quaternary ammonium salts



United States Patent PRGCEQS FUR IMPROVTNG THE HANDLE OF POLYETHYLENETEREPHTHALATE FABRIQS WTTH AN ALKALI METAL HYDRQXIDE AND SPECEFHCQUATERNARY AMMGNIUM SALTS William Graham Watson, Harrogate, England,assignor to Imperial Chemical Industries Limited, London, England, acorporation of Great Britain No Drawing. Filed Dec. 19, 1960, Ser. No.76,507 Claims priority, application Great Britain Dec. 22, 1959 7(Ilaims. (Cl. 8-4155) This invention relates to a process for treatingfabrics comprising synthetic polyester filaments or fibres in theirdrawn condition.

In British Patent No. 652,948 a process is described for producingimproved fabrics comprising treating a fabric composed of a fibreforming polyester namely highly polymerised polymethylene terephthalatehaving 2l0 inclusive carbon atoms in the polymethylene chain with anaqueous solution of caustic soda or caustic potash. The solutions maycontain 4-10% by weight of caustic alkali.

Polyethylene terephthalate filament yarn fabrics have intrinsically agood handle and draping properties, but they become harder and stiffduring finishing involving heat setting, due to the strains developedduring heat setting. Methods used commercially for softening the heatset fabrics are either, winch scouring followed by restentering at 150C., or a tratment in the presence of a dilute solution of caustic sodaas disclosed in the aforementioned British patent specification 652,948,which is carried out using a jig.

By treating the fabrics with caustic alkali, an improved handle isobtained and if the treatment is continued, sheer and thin fabrics maybe produced.

I believe that this is brought about by dissolving the polyester fromthe surface of the filaments and it can be determined by the weight lossof the filaments. The weight loss referred to, is determined by weighinga dried sample of filaments or fabrics before and after the treatmentwith the alkaline solution.

For commercial practice it is desirable to keep the concentration of thecaustic alkali as low as possible while at the same time eithermaintaining or reducing other treating conditions, e.g. time andtemperature. I have found that quite small amounts of specifiedquaternary ammonium salts, when added to caustic alkali metal hydroxidesolutions, bring about an unexpected increase in the loss of weight ofthe treated fabric. In consequence, the amount of the caustic alkali inthe treatment bath can be decreased, either while maintaining thepreviously established treating conditions or, if desired, by decreasingother treating conditions such as the time and/ or the temperature.

According to my invention, I provide a process for treating fabricscomprising synthetic polyester filaments or fibres in their drawncondition, in which the fabrics, are treated with a solution comprisinga caustic alkali metal hydroxide and a quaternary ammonium salt selectedfrom cetyl trimethyl ammonium bromide and lauryl dimethyl benzylammonium chloride.

The solutions hereinafter referred to are aqueous solutions, but itshould be appreciated that other hydroiiylated liquids, which aresoluble and miscible with water, may be used. A suitable caustic alkalihydroxide solution, which is preferred, is sodium hydroxide in water.The amount of sodium hydroxide in the solution may be 0.55%, preferably13%. Suitable amounts of the specified quaternary ammonium salt arebetween 0.005 and 0.5%, preferably 0.025 up to 0.1%.

The solutions are preferably applied at elevated temperatures of 110 C.and for treatment e.g. on a jig, between C. and the boiling point of thesolution.

The polyesters which may be treated according to my invention have aterephthaloyl group in their molecular repeat unit. They are obtainableby polycondensation from terephthalic acid with glycols having 2-10carbon atoms in their aliphatic chain, as well as from certain cyclicglycols; minor amounts of other divalent compounds coplymerisable withthe terephthaloyl group may be incorporated in amounts up to 15%, suchas isophthalic acid and sebacic acid. The polyester, for which thisinvention is particularly suitable, and which is referred to in thefollowing examples, is polyethylene terephthalate.

I have found that the effect of certain other quaternaries such as cetylpyridimium bromide, dimethyl phenyl benzyl ammonium chloride andtetramethyl-ammonium bromide is very much less marked. Moreover, somequaternary ammonium compounds crack out from the solution under treatingconditions, whereas others leave a dirty deposit on the fabric aftertreatment.

Cetyl trimethyl ammonium bromide or lauryl dimethyl benzyl ammoniumchloride, on the other hand, are very eifective, they are suitable underthe treating conditions and are commercially available in bulk at a lowcost compared with many other quaternary ammonium compounds.

In the case of low-set fabrics, my treatment may lead to thread slippagein the finished fabric. This may be minimised by embossing the fabricwith a fine overall pattern, before the treatment. This not onlyimproves the handle, but imparts greater effective cover to the fabricafter treatment. Fabrics in which thread slippage is liable to occurafter treatment are taffeta fabrics.

Yet another difficulty has been encountered in that the fabric, evenafter the caustic treatment, has been found to have a stiff handle. Ihave discovered that this is associated with inadvertent heat setting ofthe fabric under tension, which occurs e.g. while the treated fabric isdried which, in commercial practice, is done on a stenter. This secondstiffening may be overcome by dryin the fabric at a relatively lowtemperature, under C., which is insufficient to cause setting, and bykeeping the fabric not under tension during drying, or during anyoperation subsequent to the caustic treatment.

The treatment with the caustic alkali solution is conveniently carriedout on available equipment, e.g. using a jig. It is difficult, however,to obtain a uniformly treated fabric, even when the concentration andtime of treatment are accurately controlled, because temperaturevariations, particularly at the ends of the fabric occur (when using ajig), and also because it is difficult or impossible to Watch theprogress of the treatment-e.g. by determination of the weight loss inthe fabrics, without interrupting the treatment.

Instead of using a jig, in which the fabric is passed through thesolution in a trough under a pulley roller, while being unwound from afeed roller and wound up 3 on a takeup roller and back again, a requirednumber of times, an entirely different method may be used for the alkalitreatment.

This comprises winding the fabric on a perforated beam and pumping thecaustic solution through the beam under pressure to percolate thefabric, and recirculating the percolating solution for a sufiicient timeand temperature. Depending on the fabric construction, and the number oflayers wound on the beam, the pressure of the solution, which isconveniently read off between the pump and the beam gives a measure ofthe weight loss of the fabric. Moreover, the time of treatment can bereduced, compared with a treatment on a jig, because of the moreefiicient contact between the fabric and the solution under pressure.For instance, a solution containing only 1.5% sodium hydroxide and 0.05%of lauryl dimethyl benzyl ammonium chloride has given a desired weightloss of 5-10% in 2040 minutes at a temperature of only 85 C. Thiscompares most favourably with a treatment on a jig, where the time oftreatment required to achieve a comparable weight loss is 1-2 hours,using a 1.5% sodium hydroxide solution and the same amount of quaternaryammonium salt at a commercial boil (about 98100 C.).

A suitable sequence of operation for improving fabrics made from, orcontaining, a major proportion of synthetic polyester filaments orfibres in their drawn condition comprises the steps of scouring thefabric, heat setting the fabric under controlled tension on a stenter ata temperature of 7030 C. below the melting temperature of the polyester,embossing the fabric with a fine, overall embossing pattern under apressure of 10-15 tons at a temperature between at least 5 C. below theheat setting temperature and 90 C. above the second order transitiontemperature, treating the fabric with caustic alkali metal hydroxidesolution under pressure, rinsing the fabric, neutralising if necessary,with a dilute solution of acid, e.g. acetic acid, and drying the fabricat a low temperature at least 120 C. below the melting temperature ofthe polyester, preferably above 90 C., using the smallest possibletension following the treatment with the alkali solution and in allsubsequent operations including drying, to avoid stiffening of thefabric and winding the fabric Without creasing on a suitable package,such as a bobbin.

The fabrics usually require to be dyed or printed. Dyeing may be carriedout after neutralising and rinsing the fabric following the treatmentwith the caustic solution and before drying. If the fabric is to beprinted, it should be dried before printing. Drying should be carriedout at a temperature less than 130 C., in the case of polyethyleneterephthalate, and under the smallest possible tension, sufficient onlyto prevent creasing, so that the fabric does not become stiffened again.

The following examples, in which all parts and percentages are byweight, illustrate, but do not limit, my invention.

Examples 1-5 illustrate the conditions when using cetyl trimethylammonium bromide.

Examples 6-8 illustrate the use of lauryl dimethyl benzyl ammoniumchloride.

EXAMPLE 1 Samples of polyethylene terephthalate plain weave fabrics from50 denier Terylene (registered trademark) filament yarn were immersed ina glass beaker containing boiling aqueous caustic soda solution. Thesolution contained 1%, 2% or 3% by weight, of caustic soda and 0.05%cetyltrimethylammonium bromide. The samples were treated for a period of15 minutes, rinsed, and the loss in weight of the dried fabric samples,before and after the treatment, determined by weighing. Table 1summarizes the results of the treatment, which are compared with theresults obtained without the addition of the quaternary ammonium salt.

Table 1 Percent Percent Cetyl Percent loss Caustic Trimethyl in weightNo.

Soda Ammonium of fabric Bromide EXAMPLE 2 Samples of fabric as used inExample 1 were treated for 15 minutes in a beaker at the boil, and Table2 illustrates the effect of small amounts of up to 0.2% of cetyltrimethyl ammonium bromide, when added to the caustic soda solution. Itwill be seen that the eifect is most marked when the first 0.05 areadded; quantities up to 0.2% do not seem to cause a correspondingfurther increase in the loss in weight of the fabric, when the solutioncontains caustic soda of 1%, 2% and 3% by weight and when the treatingtime is only 15 minutes.

Table 2 Percent Cetyl Trimethyl Ammonium Bromide 1% NaOH 2% NaOH 3%NaOI-I Weight loss of fabric (percent) Table 3 illustrates the verymarked effect of temperature, using 3% sodium hydroxide and 0.05%cetyltrimethyl ammonium bromide for 15 minutes. The samples are the sameas described in Example 1.

Table 3 EFFECT OF TEMPERATURE OF TREATMENT BATH ON WEIGHT LOSS USING 3%NaOH +0.05 CETYL TRIMETHYL AMMONIUM BRO- MIDE IN A BEAKER FOR 15 MINUTESTemperature, C 60 70 100 Percent weight loss of fabric (percent)- 0.8 2.3 5. 5 12. 9 26.0

EXAMPLE 4 Table 4 illustrates the effect of small amounts up to 0.05% ofthe quaternary salt cetyl trimethyl ammonium bromide as used in Example1 and also the effect upon the time of the treatment for 15 minutes,compared with 30 minutes, both at C., and using 3% by Weight of aqueouscaustic soda solution.

It will be seen that even quite small amounts up to 0.05% have aconsiderable eifect on the weight loss, which increases with increasingamounts of the quaternary ammonium salt, but which does not riseconsistently with the amounts added, during a relatively short treatingtime of fifteen minutes. As the treating time is increased to 30minutes, the loss in weight is at least doubled for the Table 4 EFFECTOF QUANTITIES OF UP TO 005% OF CETYL TRI- METHYL AMMONIUM BROMIDE WHENADDED TO 3% CAUSTIC SODA SOLUTIONS-TREATED 15 MINS. AND 30 MINS. AT 95C.

7 Percent Cetyl Trimethyl Ammonium 15 mins. at Bromide 95 EXAMPLE 5Table 5 EFFECT OF TIME OF TREATMENT USING 3% NaOH+ 0.05% CETYL TRIMETHYLAMMONIUM BROMIDE FABRIC TREATED AT 98 C. ON LABORATORY WINCH Mlinutes onwinch Percent weight loss 10 6.3 12.3 19.0 26.4 '30 27.6 40 31.1

EXAMPLE 6 Samples of polyethylene terephthalate taffeta, denier 24filament, filament yarn fabric are treated in a laboratory alkaliresisting beaker with an aqueous solution containing 3% sodium hydroxideand 0.05 lauryl dimethyl benzyl ammonium chloride at 90 C., using aWater bath for heating, for 30 minutes. The weight loss of the fabric is32.2%. The treated fabric has a sheer appearance and a silky softhandle.

By comparison, samples of fabric treated under the same conditionswithout the addition of the quaternary ammonium salt show a weight lossof only 3.5%. The following table illustrates the effect of otherquaternaries under the same conditions as described in Example 6. Itwill be seen that there is no appreciable improvement, except in thecase of cetyl trimethyl ammonium bromide.

Table 6 3% SODIUM HYDROXIDE AQUEOUS SOLUTION Weight Loss after 30 mins.at 90 C.

Quaternary Ammonium Salt 0.05%

1 Fabric badly stained.

EXAMPLE 7 A 1000 yard length of a polyethylene terephthalate filamentyarn fabric, as used in Example 6, is scoured, heat set on a stenter at210 C. under controlled tension, allowing 3% relaxation in the warp andweft, the heat set fabric is embossed with a crepe design between twobowls. One of the bowls consists of annular paper washers compressedbetween solid metal discs, so that the peripheries of the paper washersform the surface of one of the bowls. The other bowl is of metal withthe crepe design engraved on it and this bowl is maintained at 210 C.During embossing a slight deformation of the filaments occurs, under apressure of 10-15 tons, as measured on hydraulic rams carrying the papersurface bowl. The embossed fabric is then treated on a jig comprising afeed roller, a trough with the solution and a trolley roller in thetrough for immersing the fabric in the solution and a wind-up roller.The trough with the solution is heated by steam injection and maintainedat -98 C. The fabric is processed by running it through the solution sixtimes which takes one hour. The solution is an aqueous solutionconsisting of 3% sodium hydroxide and 0.05%. lauryl dimethyl benzylammonium chloride in water. The Weight loss in the fabric is 6%. Thefabric is rinsed still on the jig in running water, while passing fromthe feed roll to the take-up roll and back to the feed roll. It is thenneutralised by running it through a dilute solution of acetic acid,rinsed again with water, scoured again with water containing 1 gram perlitre of a commercially available detergent consisting of a polyethyleneoxide condensate, at 9598 C., and dried. Drying of the fabric is carriedout on a pin stenter with no tension. For this purpose, the stentersetting as previously used for heat setting is slightly decreased weft-Wise, by resetting the weft pins, and the fabric is overfed on thestenter chain. The fabric is only sufiiciently tensioned at the coldpart of the stenter to allow threading up and spreading of the fabricwithout creasing between selvedges. It is then passed through driven niprolls which slightly over-feed the fabric as it is placed on thetravelling pin chains by a brush roll, so that the fabric is grippedbetween the chains at the selvedge, allowing for any Width contractionup to 1.5%. The over-feed of the nip rolls is 5%, but the actualover-feed of the fabric as placed on the stenter chains is somewhatless, about 3% because of the previous tensioning on the cold part ofthe stenter on the entry rollers, up to the nip rolls. The fabric passesthrough a heated dryingzone in which circulating air is maintained at120 C., whereby the fabric becomes dry and is taken off the pin chainsby means of a stripping bar and a second set of driven nip rolls, at theother end of the stenter, where the fabric is wound up on a suitablepackage by a surface drive from the nip rolls. The nip rolls and chainsare driven at the same surface speed. A soft uncreased and creaseresisting fabric with a very desirable soft silky handle is obtained.

Unless the above precautions during drying are taken the fabric becomesstiffened.

EXAMPLE 8 This example illustrates the use of a caustic solution withlauryl dimethyl benzyl ammonium chloride under pressure. 500 yards of ataffeta satin fabric is scoured and heat set, as described in Example 7.The fabric is a 50 denier, 24 filament, polyethylene terephthalatefilament yarn, 36" wide fabric weighing 2.43 oz. per square yard. Theheat set fabric, instead of being treated on a jig, is now wound on a 3inch diameter perforated beam on which the perforations at each end havebeen blanked off, so that the perforations extend symetrically about 1inch less than the width of the fabric, i.e. about 34 inches. Duringwinding a transverse motion is used corresponding to the width of oneselvedge of the fabric, thus avoiding a build-up of material, butensuring that when liquid is pumped through the perforated beam underpressure, it will percolate the whole width of the fabric and will notexcessively escape sideways between fabric layers and on the ends of thebeam. The beam is mounted in a closed cylinder communicating with theatmosphere through an expansion tank for pumping a caustic solutionthrough the beam and the fabric under pressure, so that the fabricbecomes immersed in the solution in the cylinder and the solution iscirculated by the pump under pressure. The caustic solution is anaqueous solution of 0.5% sodium hydroxide and 0.05% lauryl dimethylbenzyl ammonium chloride which is pumped to percolate the fabric on thebeam and continuously recycled for 30 minutes at 85 C.

The fabric is rinsed with water, acidified with dilute acetic acidscoured and rinsed again, whilst still on the beam by replacing thecaustic solution and pumping the appropriate liquids through the beamand the fabric.

The pressure measured between the pump and the beam is 18 lb. per squareinch at the beginning of the treatment with the caustic solution andthis drops to 15 lb. per square inch after 30 minutes, thus indicatingthe thinning of the fabric. The fabric is unwound from the beam anddried on the stenter, as described in Example 7. The treated fabricweight 2.3 oz. per square yard. The fabric has a softer handle and doesnot crease as before the treatment.

The differences in weight loss on four commercial runs using a beam forpercolating the liquid through the fabric under pressure showed that thelargest difference between any two pieces of fabric was less thanFabrics treated on a jig in eight runs, on the other hand, varied by asmuch as 50% in average weight loss. Moreover, the ends of the fabrictreated on the jig showed a smaller weight loss than the remainingfabric, the treatment was therefore less uniform and the ends of thefabric had a stiffer handle than the centre portion.

If it is desired to print the fabric, this is conveniently carried outafter drying, care being taken, particularly during roller printing,that no tension is applied, or only sufiicient tension to preventcreasing of the fabric.

The preceding description relates to polyethylene terephthalate filamentyarn fabrics for which our process is particularly suitable, but it isalso applicable to fabrics comprising filaments or fibres melt spun fromother synthetic polyesters or copolyesters, which contain up to of asecond component and to fabrics which may contain a minor proportion ofother fibres, e.g. cellulosic fibres, particularly flax or even cotton,but in the latter case the treatment should be limited to preventexcessive degradation of the other fibres.

What I claim is:

1. A process for improving the handle of fabrics of polyethyleneterephthalate filaments and fibers in their drawn condition whichcomprises contacting said fabrics with an aqueous solution containing0.55% of a caustic alkali metal hydroxide and 0.005-0.5% of a member ofthe group consisting of lauryl dimethyl benzyl ammonium chloride andcetyl trimethyl ammonium bromide until a portion of the surface of thefilaments has been dissolved.

2. A process for treating fabrics according to claim 1 in which thesolution comprises 13% sodium hydroxide and 0.0250.1% of the lauryldimethyl benzyl ammonium chloride.

3. A process for treating fabrics according to claim 1 in which thesolution is applied at a temperature of 4. A process for treatingfabrics according to claim 3 in which the solution is applied at atemperature between C. and the boiling point of the aqueous solution.

5. A process for treating fabrics as set forth in claim 1 in which thefabrics are treated under pressure and said solution is pumped underpressure through a plurality of layers of the fabric to percolate thefabric.

6. A process for treating fabrics according to claim 5 wherein the timeof treatment is controlled according to the drop in pressure required topump the solution through the fabric 7. A process according to claim 5in which the fabric is wound together in a helix and the said solutionis pumped under pressure from the inside of the helix to the outside.

References Cited in the file of this patent UNITED STATES PATENTS2,461,603 Hunter et al. Feb. 15, 1949 2,590,402 Hall et al. Mar. 25,1952 2,618,954 Dourdeville Nov. 25, 1952 2,670,622 Dourdeville Mar. 2,1954 2,828,528 Gajjar Apr. 1, 1958 2,852,833 Mueller Sept. 23, 19582,998,296 Hennemann Aug. 29, 1961 OTHER REFERENCES American DyestuffReporter, Nov. 28, 1949, page 862. Du Pont Bulletin D 76, March 1956,8-Teryl. McCutcheon, Soap and Chemical Specialties, December 1957, page65

1. A PROCESS FOR IMPROVING THE HANDLE OF FABRICS OF POLYETHYLENETEREPHTHALATE FILAMENTS AND FIBERS IN THEIR DRAWN CONDITION WHICHCOMPRISES CONTACTING SAID FABRICS WITH AN AQUEOUS SOLUTION CONTAINING0.5%5% OF A CAUSTIC ALKALI METAL HYDROXIDE AND 0.005-0.5% OF A MEMBER OFTHE GROUP CONSISTING OF LAURYL DIMETHYL BENZYL AMMONIUM CHLORIDE ANDCETYL TRIMETHYL AMMONIUM BROMIDE UNTIL A PORTION OF THE SURFACE OF THEFILAMENTS HAS BEEN DISSOLVED.